Pascals theorem on a hexagon inscribed in a conic
J K, L are the intersection points of opposite sides -e.g side 1 with 4, 2 with 5 and 3 with 6. And they lie on a straight line
If you pull D, E F, or G, , the hexagon changes.. If you pull C the ellipse changes as well. But the straight line remains! one had to extrapoate the 'sides" of the hexagon to make sure that the three points always show up - they could go outside the ellipse